Vertical transmission of progressive pneumonia of sheep.

: Forty-two lambs were derived by hysterectomy from 27 ewes. Eight ewes had lesions of chronic progressive pneumonia (CPP) and 19 did not. Eleven lambs were derived from ewes with lesions of CPP. These 11 lambs were maintained in isolators under germfree conditions until killed at 2 to 4 months of age. Lungs from each lamb were examined for gross and microscopic lesions of CPP and examined by microbiological cultural technique (blood, eosin methylene blue, and PPLO agar). The lungs of one 4-month-old lamb from a ewe infected with CPP had foci of gray consolidation in the apical and cardiac lobes. The microscopic changes were comparable to those in the dam. The lungs of a 2.5-month-old lamb from a ewe infected with CPP had lymphocytic accumulations in the alveolar walls and around blood vessels and bronchioles. The 9 other lambs were free of lesions. Neither bacteria nor mycoplasmas were isolated from any of the 11 lambs. Lesions of CPP were not found in 31 lambs from the 19 noninfected ewes.